Methods For Carrying And Transmitting 3D Z-Norm Attributes In Digital TV Closed Captioning

ABSTRACT

Methods for carrying and transmitting overlay depth data of an overlay of a stereoscopic image of a display device as a fraction of a viewer distance from the overlay are described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/311,742 filed Mar. 8, 2010, hereby incorporated by reference inits entirety.

The present application is related to PCT Application PCT/U.S.2010/039543 for ‘Perceptual Depth Placement For 3D Objects’ by RichardWelsh and Christian Ralph, filed on Jun. 22, 2010 incorporated herein byreference in its entirety and attached herewith as Appendix A.

FIELD

The present disclosure relates to carriage of the z-norm depthinformation of the overlay. In particular, it relates to methods forcarrying and transmitting 3D z-norm attributes in digital tv closedcaptioning.

BACKGROUND

The CEA-708-D standard (see, e.g.,http://www.ce.org/Standards/browseByCommittee_(—)2525.asp, incorporatedherein by reference in its entirety) defines Digital TV closedcaptioning as used in Digital TV systems (ATSC, DVB, Cable), etc. NewerDigital TV systems provide a 3D rendering capability which provides fordepth projection of Video content during playback through use ofpolarized glass and lens technology and/or shuttered glasses.

One problem present in such systems today is that there does not exist ameans to specify, using existing CEA-708D captioning technology, thedepth for which the on-screen display of caption data shall be rendered.

SUMMARY

According to a first aspect, a method for carrying data is provided,comprising: providing overlay depth data of an overlay of a stereoscopicimage of a display device as a fraction of a viewer distance from theoverlay; and allocating the overlay depth data in an available portionof a layer of a multilayer protocol system for transmission of overlays.

According to a second aspect, a method to transmit data to a clientdevice is provided, comprising: providing overlay depth data of anoverlay of a stereoscopic image of a display device as a fraction of aviewer distance from the overlay; coding the overlay depth data in anavailable portion of a layer of a multilayer protocol system fortransmission of overlays; and transmitting the coded overlay depth datato the client device.

Therefore, in accordance with several embodiments of the presentdisclosure, means to extend the CEA-708-D closed caption standard are tosupport depth adjustment for the end user system.

APPENDIX

Appendix A is attached herewith and forms integral part of thespecification of the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of an embodiment of the methods in accordancewith the disclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Generation of normalized depth data on the z-axis is described in PCTApplication PCT/U.S. 2010/039543 attached herewith as Appendix A. Suchz-norm depth information can also apply to overlay and, in particular,to close captioning.

Embodiments of the present disclosure are directed to carriage of thez-norm depth information of the overlay. In particular, such informationcan be conveyed through unallocated elements of a closed captionsstandard, such as the CEA-708-D standard.

The closed captioning standard CEA-708-D defines a closed-caption systemfor digital television (DTV) using the OSI layered protocol model (see,e.g., http://en.wikipedia.org/wiki/OSI_model, incorporated herein byreference in its entirety). As such, the transport, packet, service,coding, and interpretation layer are all used by the standard. Thestructure of these layers is known to the person skilled in the art andwill not be discussed in detail in the present application.

As shown in the examples below, the z-norm depth information can becoded in an available portion of a service layer, coding layer, packetlayer etc. of the standard. On the client side, the client device (e.g.,set-top box, television, personal computer and the like) can contain asoftware modification that permits dynamic 3D processing of the overlay.

The choice and selection of the layer (e.g., packet, service, coding) bywhich the depth information is communicated and the type ofinterpretation provided by the interpretation layer may be applicationspecific.

EXAMPLE 1 Packet Layer

For the packet layer definition, reference can be made to the cc_data()structure as defined in section 4.4 of CEA-708-D standard (DTV cc-data( )structure), incorporated herein by reference in its entirety. Inaccordance with the present disclosure, such a structure can beaugmented such that one possible example of such an implementation wouldresult in cc_data.reserved (8 bits) encodes the Z-Norm data as definedbelow:

reserved<7>=sign bit

reserved<6-0>=znorm value

The person skilled in the art will understand that other packet layerimplementations are possible.

This packet layer embodiment allows for carriage of z-norm depth data ona per-packet basis. It should be noted that these bit definitions arecurrently reserved and set to all 1's. Therefore, such modification doesnot break existing compatibility with legacy systems.

EXAMPLE 2 Service Layer

The DTV closed captioning standard CEA-708-D provides for up to 63services. The services are time division multiplexed and insertedsequentially into caption channel packets (coding layer). Service #1 isthe primary caption service while Service #2 provides for the secondarylanguage service. Service #0 is not to be used. Service #1-6 arestandard services and Services #7-#63 are extended services.

According to an embodiment of the present disclosure, a service # can beallocated from one of the extended services #7-#63.

For packing of z-norm data within a service channel, the service blockdefinition of section 6.2 in CEA-708-D (6.2 Service Blocks, incorporatedherein by reference in its entirety) can be used, with a service channelpacket using an extended_service_number and block_size=1.

The format of the block_data[0] byte within the extended service packetcan be similar to what shown in Example 1 above:

block_data[0].<7>=sign bit

block_data[0].reserved<6-0>=znorm value

allowing for up to 64 signed and unsigned znorm correction values to becommunicated to the DTV rendering device on a per-service basis. Theperson skilled in the art will understand that the above implementationcould be done at different levels of the CC service protocol stack. Theexemplary implementation above was chosen by applicants to support thebroadcast compatibility across existing (Legacy) set-top box receiversand televisions.

EXAMPLE 3 Coding Layer

For packing of Z-Norm data within the coding layer of CEA-708-D, any ofthe unused codes as defined in section 7 of CEA-708-D (7 DTVCC CodingLayer—Caption Data Services (Services 1-63), incorporated herein byreference in its entirety) can be used. One or more bytes of data can besupported using the 1, 2, or 3-byte character code extensions.

For optimal compatibility, the extended code space in section 7.1.1(7.1.1 Extending The Code Space) can be used with a minimum of a 1-bytecode from the C1 Code set defined in 7.1.5 (7.1.5 C1 Code Set—CaptioningCommand Control Codes). For example, a window command is a single bytethat may be followed by several parameter bytes. In a similar fashion, az-norm depth command may be defined as a one of the undefined windowcommands 0×93-0×96 which carries the z-norm bits as defined below:

znorm_direction<7>=sign bit

znorm_value<6-0>=znorm value

It should be noted however, that additional information may be conveyedbeyond just the Z-Norm shift offset and sign (positive/negativedirection). However, at the time of this writing the above requirementsshould meet the majority of existing TV platforms supportingstereoscopic display capabilities however, without loss of generality,additional fields may be encapsulated in this proposed schema.

The person skilled in the art will understand that, for all of theexamples provided above, the bit definition may change to allow for lessdepth information to be carried since most current displays do not allowfor more than 15 pixel offset correction to be performed. The presentdisclosure is intended to cover any and all definitions for these bits,with the main concepts of the disclosure allowing for any embodiment orderivative of the same to be covered across all layers of the transportmedium.

Therefore, in accordance with several embodiments of the presentdisclosure, a method (100) as disclosed in the flowchart of FIG. 1.Overlay depth data are provided (110) and allocated and/or coded (120)in an available portion of a protocol system such as a protocoloperating according to a CEA-708-D standard. The overlay depth data canthen be transmitted (130) to a client device and processed (140) at suchdevice.

The present disclosure may suitably comprise, consist of, or consistessentially of, any element (the various parts and/or features of thedisclosure) and their equivalents as described herein. Further,embodiments of the present disclosure may be practiced in the absence ofany element, whether or not specifically disclosed herein. Numerousmodifications and variations of the disclosure are possible in light ofthe above teachings. It is therefore to be understood that within thescope of the appended claims, the disclosure may be practiced otherwisethan as specifically described herein.

1. A method for carrying data, comprising: providing overlay depth dataof an overlay of a stereoscopic image of a display device as a fractionof a viewer distance from the overlay; and allocating the overlay depthdata in an available portion of a layer of a multilayer protocol systemfor transmission of overlays.
 2. The method of claim 1, wherein theoverlay depth data are close captioning depth data and the multilayerprotocol system for transmission of overlays is a multilayer protocolsystem for transmission of close captioning.
 3. The method of claim 2,wherein the multilayer protocol system for transmission of closecaptioning operates according to a CEA-708-D standard.
 4. The method ofclaim 2, wherein the available portion is a portion of a packet layer ofthe multilayer protocol system.
 5. The method of claim 4, wherein themultilayer protocol system for transmission of close captioning operatesaccording to a CEA-708-D standard and wherein an augmented cc_data ( )structure is provided to carry the overlay depth data.
 6. The method ofclaim 5, wherein a first section of the augmented cc_data( )structurecarries a sign bit and a second section of the augmented cc_data()structure carries a binary value of the overlay depth data.
 7. Themethod of claim 2, wherein the available portion is a portion of aservice layer of the multilayer protocol system.
 8. The method of claim7, wherein the multilayer protocol system for transmission of closecaptioning operates according to a CEA-708-D standard and whereinextended services are adopted to carry the overlay depth data.
 9. Themethod of claim 8, wherein the extended services are selected betweenservice #7 and service #73.
 10. The method of claim 8, wherein theextended services comprise a size portion and a data portion, andwherein a first section of the data portion carries a sign bit and asecond section of the data portion carries a binary value of the overlaydepth data.
 11. The method of claim 2, wherein the available portion isa portion of a coding layer of the multilayer protocol system.
 12. Themethod of claim 11, wherein the multilayer protocol system fortransmission of close captioning operates according to a CEA-708-Dstandard and wherein the overlay depth data are supported through1-byte, 2-byte or 3-byte character code extensions.
 13. The method ofclaim 12, wherein the overlay depth data are supported through anundefined window command.
 14. The method of claim 13, wherein the windowcommand is selected between window commands 0×93 and 0×96.
 15. Themethod of claim 14, wherein a first section of the window commandcarries a sign bit and a second section of the window command carries abinary value of the overlay depth data.
 16. A method to transmit data toa client device, comprising: providing overlay depth data of an overlayof a stereoscopic image of a display device as a fraction of a viewerdistance from the overlay; coding the overlay depth data in an availableportion of a layer of a multilayer protocol system for transmission ofoverlays; and transmitting the coded overlay depth data to the clientdevice.
 17. The method of claim 16, wherein the client device isselected from set-top box, television and personal computer.
 18. Themethod of claim 16, wherein the client device processes the codedoverlay depth data.